I run Firefox from a Flatpak but I can't find how to have it open links when I click them in various XDG-compliant apps. How can I have xdg-open run Firefox from a Flatpak distribution?
The application itself shows in preferences that it is not the default browser. It offers a button to set itself as default but it seems to have no effect.
You need to use the xdg-settings command. This should return your current default browser:
xdg-settings get default-web-browser
To change it to your Flatpak version, do this:
xdg-settings set default-web-browser <your_flatpak_browser.desktop>
To validate your new settings, do this:
xdg-settings check default-web-browser <your_flatpak_browser.desktop>
/var/lib/flatpak/exports/share/applications/org.mozilla.firefox.desktop.
xdg-settings set default-web-browser org.mozilla.firefox.desktop managed to install it.
xdg-settings set default-web-browser com.brave.Browser.desktop WFM
In addition to the above posted:
xdg-settings set default-web-browser <your_flatpak_browser.desktop>
the following settings helped me:
xdg-mime default <your_flatpak_browser.desktop> x-scheme-handler/https x-scheme-handler/http
E.g.:
xdg-mime default org.mozilla.firefox.desktop x-scheme-handler/https x-scheme-handler/http
xdg-settings set default-web-browser org.mozilla.firefox.desktop
For Linux Mint (21.2), the best way to set a flatpak-installed Firefox as the default browser was within Default Applications, Web Browser, then select "Other..." and enter
flatpak run org.mozilla.firefox "%s"
